The majority of the FIC indices were in the range of 0.5–2.0; therefore, the main interaction between the samples and the three antibiotics was considered to be additive. However, gallic acid was the only compound that showed any antagonistic action to the b-lactam antibiotics. Only oxacillin and penicillin G were antagonized and antagonism was demonstrated by only one of the 17 MRSA strains. With all other strains, gallic acid had an additive action with all three antibiotics and no synergistic action. The effect of tannic acid and the b-lactams was very similar to that of gallic acid and the b-lactams, in that an additive effect was observed with most strains except for three that showed a synergistic effect with amoxicillin only. A synergistic reaction of the ethanol extract and ethyl acetate fraction with b-lactams was obtained. A synergistic response with amoxicillin was obtained with 76% and 59% of strains respectively, for oxacillin 12% and 35% of strains and for penicillin G, 53% and 12% of strains respectively. For all other strains the responses were additive.